This is not hard. Use the open collector accessory port outputs to encode the correct Yaesu BCD band data signals (signals A, B, C and D on your amplifier connectors). These are controlled in Setup > General > ANAN Ctrl. Click the "Ext Control" button to enable them, then program them as required.

You will then need to create an interface circuit card that implements 5VDC pull-up resistors on each of the 4 signals. When a box is checked in PowerSDR ANAN Ctrl setup that signal will be pulled to ground by a FET in the radio, i.e. logic zero. When a box is not checked the FET in the radio will not conduct, allowing the pull up resistor to pull that line up to 5VDC, i.e. logic one.

Get your wiring straight, board with 4 resistors and a 5V voltage regulator built, and the checkmarks in the right boxes and it'll all work. A fun, easy and classic ham radio project.

I have a Quadra in my station. Whilst testing various ANAN radios, I have avoided using them as exciters for the Quadra because they are not fitted with an ALC input and I do not feel comfortable operating the Quadra without a properly-connected and calibrated ALC loop.

va7oj wrote:I have a Quadra in my station. Whilst testing various ANAN radios, I have avoided using them as exciters for the Quadra because they are not fitted with an ALC input and I do not feel comfortable operating the Quadra without a properly-connected and calibrated ALC loop.

That seems a bit overly cautious, Adam. Do you not trust the built in overdrive protection features of the Quadra in case of an operator error? What amp's do you think are safe to use with openHPSDR hardware?

I have yet to hear of anyone blowing up an amp due to lack of an ALC function on openHPSDR architecture hardware (that include Apache Labs/PowerSDR configurations). Of course most modern solid state amp's have excellent protection features and most tube rigs are pretty bulletproof. Is the Quadra design old enough to be in some funny middle ground where amp protection features on solid state amp's are not reliable or effective?

IMHO, the lack of ALC in the openHPSDR architecture motivates proper operation. That, combined with linearization, really makes it tough to "get loud" in old school fashion, i.e. by compressing the crap out of the external high power amplifier (and throwing massive quantities of IMD all over the band).

In the Quadra, ALC voltage is derived from forward and reflected power. Initially, the user adjusts the ALC menu item in the Quadra such that the output levels off at the design output rating (1kW, or 500W in LOW mode). The next step is to adjust the drive power (exciter output) for a very slight drop in amplifier output. This is the correct operating point for the Quadra, which will avoid "ALC compression" such as you describe.

If load VSWR > 1.5:1, the Quadra will develop ALC voltage which will throttle back the drive to avoid possible damage to the amplifier's harmonic filters or power devices. In the event of sudden extreme overdrive or a catastrophic failure of the antenna/feedline system, the amplifier's internal overdrive or mismatch protection circuits will force the Quadra into standby, but the ALC will also reduce drive so as to decrease the possibility of hot-switching the T/R relays during the shutdown operation.

All commercial and mil/gov HF radio systems are equipped with an ALC loop. During the initial self-test cycle in some modern systems, the start-up sequence will abort unless the ALC line is connected. William Sabin, in "HF Radio Systems & Circuits", states clearly that some form of ALC should always be provided. We included ALC in the HF systems with which I worked at Racal in the 1960's, and I have been using solid-state amplifiers (always with ALC) in my amateur station for 30 years. I do not see a problem with this.

A learning process is required of the operator. Just as we need to learn how to manage front-end gain in a direct-sampling SDR so as to optimise receiver performance, we also need to learn how to set drive power in an ALC-equipped transmitter with an external HPA. (Yes, am aware of old dogs and new tricks, but learning new things has never been an issue for me.)

A tube amplifier, either grid-driven and swamped or cathode-driven with lots of grid dissipation reserve, should be OK for use with an exciter not fitted with ALC. I stand by my advocacy of ALC in my above-referenced article.

That's a lot of words to say "I like ALC and think it's an important amplifier and radio function."

I don't agree. ALC is completely unnecessary convenience feature as long as the amp has sufficiently effective overdrive and VSWR protection, to include prohibitions on hot switching. There are many current designs that offer this level of protection.

More importantly, the PureSignal linearization algorithm will not run well or possibly at all with ALC. ALC will be a so-called "memory effect" of such magnitude that the algorithm will, at best, demonstrate an oscillation between two states, much as is seen with the few amp's that utilized adaptive bias controls. This latter issue alone would be sufficient to see me disabling ALC even if the radio hardware supported it. To be fair, one can set things up to stay safely below any ALC action, but that will not allow easy use of 100% of the amplifier's performance.

At any rate, one way or the other, many people are 100% successful running pretty much every amplifier out there with Apache hardware and no ALC. I'd suggest anyone reading this not be scared off or even slightly concerned by lack of ALC.